Looking for replacement sliding glass door wheels

Thanks for posting. I believe this is just the inner portion of a roller assembly. The outer housing may still be lodged in the door. If you could extract this and show us the entire roller, we should be able to narrow down what you need. 

That's definitely the outer housing I see in these photos, but it's not possible to identify it unless its uninstalled. 

It does appear that you have an aluminum door, unless I'm mistaken. If so then it may be necessary to knock the bottom rail off the door. This can be done with a wooden block and mallet, after you remove the installation screw. It will take firm, but gentle, taps; the last thing you want to do is damage the glass.

This is a big project. You'll probably want an extra pair of hands at the very least, and an afternoon to do it. At this stage you may even want to consider the help of a local professional do to it for you. 

You should also note that replacement parts for older aluminum doors like this aren't always available. We carry a wide selection of rollers, so there's a good chance we have a match for this part, but you should understand that this isn't a guarantee. I'll only know for sure when I see that housing out of the door.